1. Field of the Invention
The present invention relates to a measuring apparatus with which a position or a position and a posture of an object to be measured can be measured, and a method for correcting errors in position or position and posture of an end effecter of a machine for controlling positions and postures of the end effecter by means of an actuator.
2. Prior Art
It is the case with machines such as machine tools or robots for controlling positions and postures of a main shaft, a tool, a hand or other members (hereinafter referred to in summary as xe2x80x9cend effecterxe2x80x9d) by means of an actuator that it is extremely difficult to set geometrical errors of the its mechanism to zero or to measure them, and errors were included in positions and postures of the end effecter by the influence of these errors. For correcting such errors in positions and postures of the end effecter in Japanese Patent Application Laid-Open Publication No. 4-211806 (1992), an end effecter of a robot is positioned at a fixture having a plurality of known reference points, a prevailing position is detected by means of a position detector provided in the robot, a geometrical error of the mechanism of the robot is estimated based on a shift of the detected position from a preliminarily measured reference point, and by correcting this error, an error in position and posture of the end effecter is accordingly corrected.
However, in performing correction of errors in positions and postures of the end effecter of the above robot, drawbacks were presented in that the fixture needed to be manufactured at high accuracy and in that high accuracy positioning of the end effecter of the robot to the fixture was difficult. Further, there was no compact measuring apparatus available for measuring positions and postures of objects to be measured that are supported by another member such as the end effecter.
The present invention has been made in view of the above problems, and it is a first object thereof to provide a highly accurate and compact measuring apparatus that is capable of measuring positions and postures of an object to be measured that is supported by another member.
It is a second object of the present invention to provide a method for correcting errors in a machine capable of controlling positions and postures of an end effecter by means of an actuator wherein geometrical errors of a mechanism of the machine is estimated and corrected based on a measured value obtained by a measuring device that is capable of measuring;distances between the end effecter and a fixing portion of the machine and of measuring positions or positions and postures of an end effecter for correcting errors in positions and postures of the end effecter.
For solving the above subjects, the invention according to a first embodiment comprises first universal joints, first fixing members to which the first universal joints are attachable, a base to which at least three of the first fixing members are attached, a second universal joint, a second fixing member that is attached to an object to be measured and to which the second universal joint is attachable, and a measuring device that is attached to between the at least three first universal joints that are attached to the base by means of the first fixing members and the second universal joint that is attached to the object to be measured by means of the second fixing member, wherein a position of the object to the measured with respect to the base is measured by measuring distances between the at least three first universal joints and the second universal joint.
The invention according to a second embodiment comprises a first universal joint, a first fixing member to which the first universal joint is attachable, a table that is mounted on a base, to which the first fixing member is attachable and that is arbitrarily positionable on a plane, a driving device for driving the table for positioning, a detecting device for detecting a position of the table, a second universal joint, a second fixing member that is attached to an object to be measured and to which the second universal joint is attachable, and a measuring device that is attached to between the first universal joint that is attached to the table by means of the first fixing member and the second universal joint that is attached to the object to be measured by means of the second fixing member, wherein a position of the object to be measured with respect to the base is measured by positioning the first universal joint at least at three points by moving the table and measuring distances between the first universal joint at the respective positions and the second universal joint.
The invention according to a third embodiment comprises first universal joints, first fixing members to which the first universal joints are attachable, a base to which at least three of the first fixing members are attached, second universal joints, a second fixing member that is attached to an object to be measured and to which at least three second universal joints are attachable, and a measuring device that is attached to between the at least three first universal joints that are attached to the base by means of the first fixing members and the at least three second universal joints that are attached to the object to be measured by means of the second fixing member, wherein a position and a posture of the object to be measured with respect to the base is measured by respectively measuring distances between the at least three first universal joints and the at least three second universal joints.
The invention according to a fourth embodiment comprises a first universal joint, a first fixing member to which the first universal joint is attachable, a table that is mounted on a base, to which the first fixing member is attachable and that is arbitrarily positionable on a plane, a driving device for driving the table for positioning, a detecting device for detecting a position of the table, second universal joints, a second fixing member that is attached to an object to be measured and to which at least three second universal joints are attachable, and a measuring device that is attached to between the first universal joint that is attached to the table by means of the first fixing member and the at least three second universal joints that are attached to the object to be measured by means of the second fixing member, wherein a position and a posture of the object to be measured with respect to the base is measured by positioning the first universal joint at least at three points by moving the table and measuring distances between the first universal joint at the respective positions and the at least second universal joints.
The invention according to a fifth embodiment first universal joints, first fixing members to which the first universal joints are attachable, a base to which at least three of the first fixing members are attached, a second universal joint, a second fixing member that is attached to an object to be measured as to be capable of being rotated and indexed and to which the second universal joint is attachable in an eccentric manner with respect to a central axis of rotating, and a measuring device that is attached to between the at least three first universal joints that are attached to the base by means of the fixing members and the second universal joint that is attached to the object to be measured by means of the second fixing member, wherein a position and a posture of the object to the measured with respect to the base is measured by positioning the second universal joint at least at three points by rotational movement of the second fixing member and by measuring distances between the second universal joint and at least three first universal joints.
The invention according to a sixth embodiment comprises a first universal joint, a first fixing member to which the first universal joint is attachable, a table that is mounted on a base, to which the first fixing member is attachable and that is arbitrarily positionable on a plane, a driving device for driving the table for positioning, a detecting device for detecting a position of the table, second universal joints, a second fixing member that is attached to an object to be measured and to which at least three second universal joints are attachable, and a measuring device that is attached to between the first universal joint that is attached to the table by means of the first fixing member and the at least three second universal joints that are attached to the object to be measured by means of the second fixing member, wherein a position and a posture of the object to be measured with respect to the base is measured by positioning the first universal joint at least at three points by moving the table and measuring distances between the first universal joint at the respective positions and the at least second universal joints.
The invention according to a seventh embodiment is related to a method for correcting errors between command values and actual positions and postures of a base and an end effecter that is provided to be movable and positionable with respect to the base, wherein the error correcting method includes the steps of positioning the end effecter at a plurality of arbitrary positions and postures, measuring a distance between a single point on the end effecter and a single point on the base, estimating geometric errors of an apparatus for controlling positions and postures of the end effecter by means of an actuator such that differences between values obtained by measuring the distance between the two points from among the plurality of arbitrary positions and postures and the command values become minimum, and correcting errors of the positions and postures of the end effecter by setting these geometric errors as correction values.
The invention according to an eighth embodiment is related to a method for correcting errors between command values and actual positions and postures of a base and an end effecter that is provided to be movable and positionable with respect to the base, wherein the error correcting method includes the steps of positioning the end effecter at a plurality of arbitrary positions and postures, respectively measuring distances between a single point on the end effecter and three points on the base, obtaining positions of the end effecter among the plurality of arbitrary positions based on the measured value, estimating geometric errors of an apparatus for controlling positions and postures of the end effecter by means of an actuator such that differences between values obtained by measuring the distance between the two points from among the plurality of arbitrary positions and postures and the command values become minimum, and correcting errors of the positions and postures of the end effecter by setting these geometric errors as correction values.
The invention according to a ninth embodiment is related to a method for correcting errors between command values and actual positions and postures of a base and an end effecter that is provided to be movable and positionable with respect to the base, wherein the error correcting method includes the steps of positioning the end effecter at a plurality of arbitrary positions and postures, respectively measuring distances between three points on the end effecter and three points on the base, obtaining positions of the end effecter among the plurality of arbitrary positions based on the measured value, estimating geometric errors of an apparatus for controlling positions and postures of the end effecter by means of an actuator such that differences between values obtained by measuring the distance between the two points from among the plurality of arbitrary positions and postures and the command values become minimum, and correcting errors of the positions and postures of the end effecter by setting these geometric errors as correction values.